1. Technical Field
The present invention relates to a video display apparatus constructed using a liquid crystal panel and a backlight, and more specifically relates to a backlight luminance control apparatus which adjusts the quality of a video image by controlling the luminance distribution of the backlight and the video display apparatus.
2. Description of Related Art
Conventionally, liquid crystal displays are widely used as video display apparatuses, such as monitor devices for computers, and television receivers. A liquid crystal display is constructed using a liquid crystal panel and a backlight for illuminating the liquid crystal panel from the back side, and displays a video image by controlling light from the backlight to be transmitted or blocked in each portion on the liquid crystal panel. Although many backlights use fluorescent tubes as their light sources, a backlight using light emitting diodes (LEDs) as the light source has also been developed. Japanese Patent Application Laid-Open No. 2007-219234 discloses a video display apparatus using LEDs as the light source of the backlight.
A backlight using LEDs is constructed by arranging a large number of LEDs in a plane, and placed on the back side of the liquid crystal panel. The backlight is segmented into a plurality of areas which illuminate different positions on the liquid crystal panel, and the video display apparatus is capable of controlling the luminance in each area of the backlight individually. Each area of the backlight includes a plurality of LEDs and illuminates a portion of the liquid crystal panel. A video image displayed by the video display apparatus usually includes a relatively bright portion and a relatively dark portion. A portion of the liquid crystal panel which displays a bright portion of the video image needs to be illuminated by the backlight with high luminance, while the backlight can have lower luminance for a portion of the liquid crystal panel which displays a dark portion of the video image. Thus, by adjusting the luminance in each area of the backlight individually to increase the luminance in an area illuminating a portion of the liquid crystal panel which displays a bright portion of the video image and decrease the luminance in an area illuminating a portion which displays a dark portion, it is possible to reduce the power consumption of the video display apparatus while securing necessary luminance.